Modified natural killer cells and natural killer cell lines having increased cytotoxicity

ABSTRACT

NK cells and NK cell lines are modified to increase cytotoxicity, wherein the cells and compositions thereof have a use in the treatment of cancer. Production of modified NK cells and NK cell lines is via genetic modification to remove checkpoint inhibitory receptor expression and/or add mutant (variant) TRAIL ligand expression.

CROSS-REFERENCE

This application is a continuation of International Application Ser. No.PCT/EP2016/068001, filed Jul. 29, 2016, which claims the benefit of andthe right of priority to United Kingdom Application Nos. 1610164.4 filedJun. 10, 2016; 1603655.0 filed Mar. 2, 2016; GB1605457.9 filed Mar. 31,2016; and European Application No. 15178899.9, filed Jul. 29, 2015,which applications are incorporated herein by reference in theirentirety.

INTRODUCTION

The present invention relates to the modification of natural killer (NK)cells and NK cell lines to produce derivatives thereof with a morecytotoxic phenotype. Furthermore, the present invention relates tomethods of producing modified NK cells and NK cell lines, compositionscontaining the cells and cell lines and uses of said compositions in thetreatment of cancer.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted electronically in ASCII format and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Jul. 29, 2016 isnamed 51304701301_SL.txt and is 28 kilobytes in size.

BACKGROUND OF THE INVENTION

Typically, immune cells require a target cell to present antigen viamajor histocompatibility complex (MHC) before triggering an immuneresponse resulting in the death of the target cell. This allows cancercells not presenting MHC class I to evade the majority of immuneresponses.

NK cells are able, however, to recognize cancer cells in the absence ofMHC class I expression. Hence they perform a critical role in the body'sdefense against cancer.

On the other hand, in certain circumstances, cancer cells demonstrate anability to dampen the cytotoxic activity of NK cells, through expressionof ligands that bind inhibitory receptors on the NK cell membrane.Resistance to cancer can involve a balance between these and otherfactors.

Cytotoxicity, in this context, refers to the ability of immune effectorcells, e.g. NK cells, to induce cancer cell death, e.g. by releasingcytolytic compounds or by binding receptors on cancer cell membranes andinducing apoptosis of said cancer cells. Cytotoxicity is affected notonly by signals that induce release of cytolytic compounds but also bysignals that inhibit their release. An increase in cytotoxicity willtherefore lead to more efficient killing of cancer cells, with lesschance of the cancer cell dampening the cytotoxic activity of the NK, asmentioned above.

Genetic modification to remove inhibitory receptor function on NK cellshas been suggested as a method for increasing the cytotoxicity of NKcells against cancer cells that lack MHC class I expression but are ableto dampen NK cytotoxicity (Bodduluru et al. 2012). NKG2A has beenestablished as an inhibitory receptor worth silencing under thesecircumstances, as certain cancer cells are known to express MICA whichbinds NKG2A and inhibits NK cell cytotoxicity in the absence of MHCclass I expression (Shook et al. 2011; WO 2006/023148).

Another method of downregulating NKG2A expression has been shown inNK-92 cells, in which transfection with a gene encoding IL-15 was shownto be associated with a reduction in NKG2A expression (Zhang et al.2004). However, despite an observed increase in the cytotoxicity of theNK cells, the increase was likely a result of a concomitant increase inexpression of the activating receptor NKG2D. This is supported by theobservation that blocking NKG2A receptors on NK-92 cells was notassociated with an increase in cytotoxicity against multiple myelomacells (Heidenreich et al. 2012). Nevertheless, it is worth noting thatthe NK-92 cell line is a highly cytotoxic cell line with very lowexpression of inhibitory receptors. Therefore, any increase incytotoxicity associated with decreased NKG2A expression might have beentoo trivial to detect.

Similar studies have been carried out in mice. For example, mice expressa receptor called Ly49 on NK cells, which is analogous to humaninhibitory KIR receptors. It has been shown that by blocking the Ly49receptor with antibody fragments, NK cells are more cytotoxic andcapable of killing murine leukemia cells in vitro and in vivo (Koh etal. 2001).

It is a consequence of reducing inhibitory receptor function, however,that ‘normal’ cells in the body also become more susceptible to attackby modified NK cells, as the modified NK cells become less capable ofdistinguishing between ‘normal’ cells and cancer cells. This is asignificant disadvantage of reducing ‘classical’ inhibitory receptorfunction.

Another way in which NK cells are known to kill cancer cells is byexpressing TRAIL on their surface. TRAIL ligand is able to bind TRAILreceptors on cancer cells and induce apoptosis of said cancer cells. Onespeculative approach describes overexpressing TRAIL on NK cells, inorder to take advantage of this anti-cancer mechanism (EP1621550).Furthermore, IL-12 has been reported to upregulate TRAIL expression onNK cells (Smyth et al. 2001).

Nevertheless, cancer cells have developed evasive and protectivemechanisms for dealing with NK cells expressing TRAIL. Decoy TRAILreceptors are often expressed on cancer cell membranes, and binding ofTRAIL to these decoy receptors is unable to induce apoptosis; methods ofovercoming such mechanisms have not yet been pursued.

Acute myeloid leukemia (AML) is a hematopoietic malignancy involvingprecursor cells committed to myeloid development, and accounts for asignificant proportion of acute leukemias in both adults (90%) andchildren (15-20%) (Hurwitz, Mounce et al. 1995; Lowenberg, Downing etal. 1999). Despite 80% of patients achieving remission with standardchemotherapy (Hurwitz, Mounce et al. 1995; Ribeiro, Razzouk et al.2005), survival remains unsatisfactory because of high relapse ratesfrom minimal residual disease (MRD). The five-year survival isage-dependent; 60% in children (Rubnitz 2012), 40% in adults under 65(Lowenberg, Downing et al. 1999) and 10% in adults over 65 (Ferrara andSchiffer 2013). These outcomes can be improved if patients have asuitable hematopoietic cell donor, but many do not, highlighting theneed for an alternative approach to treatment.

Natural killer (NK) cells are cytotoxic lymphocytes, with distinctphenotypes and effector functions that differ from e.g. natural killer T(NK-T) cells. For example, while NK-T cells express both CD3 and T cellantigen receptors (TCRs), NK cells do not. NK cells are generally foundto express the markers CD16 and CD56, wherein CD16 functions as an Fcreceptor and mediates antibody dependent cell-mediated cytotoxicity(ADCC) which is discussed below. KHYG-1 is a notable exception in thisregard. Despite NK cells being naturally cytotoxic, NK cell lines withincreased cytotoxicity have been developed. NK-92 and KHYG-1 representtwo NK cell lines that have been researched extensively and show promisein cancer therapeutics (Swift et al. 2011; Swift et al. 2012).

Adoptive cellular immunotherapy for use in cancer treatment commonlyinvolves administration of natural and modified T cells to a patient. Tcells can be modified in various ways, e.g. genetically, so as toexpress receptors and/or ligands that bind specifically to certaintarget cancer cells. Transfection of T cells with high-affinity T cellreceptors (TCRs) and chimeric antigen receptors (CARs), specific forcancer cell antigens, can give rise to highly reactive cancer-specific Tcell responses. A major limitation of this immunotherapeutic approach isthat T cells must either be obtained from the patient for autologous exvivo expansion or MHC-matched T cells must be used to avoidimmunological eradication immediately following transfer of the cells tothe patient or, in some cases, the onset of graft-vs-host disease(GVHD). Additionally, successfully transferred T cells often survive forprolonged periods of time in the circulation, making it difficult tocontrol persistent side-effects resulting from treatment.

In haplotype transplantation, the graft-versus-leukemia effect isbelieved to be mediated by NK cells when there is a KIR inhibitoryreceptor-ligand mismatch, which can lead to improved survival in thetreatment of AML (Ruggeri, Capanni et al. 2002; Ruggeri, Mancusi et al.2005). Furthermore, rapid NK recovery is associated with better outcomeand a stronger graft-vs-leukemia (GVL) effect in patients undergoinghaplotype T-depleted hematopoietic cell transplantation (HCT) in AML(Savani, Mielke et al. 2007). Other trials have used haploidentical NKcells expanded ex vivo to treat AML in adults (Miller, Soignier et al.2005) and children (Rubnitz, Inaba et al. 2010).

Several permanent NK cell lines have been established, and the mostnotable is NK-92, derived from a patient with non-Hodgkin's lymphomaexpressing typical NK cell markers, with the exception of CD16 (Fc gammareceptor III). NK-92 has undergone extensive preclinical testing andexhibits superior lysis against a broad range of tumors compared withactivated NK cells and lymphokine-activated killer (LAK) cells (Gong,Maki et al. 1994). Cytotoxicity of NK-92 cells against primary AML hasbeen established (Yan, Steinherz et al. 1998).

Another NK cell line, KHYG-1, has been identified as a potentialcontender for clinical use (Suck et al. 2005) but has reducedcytotoxicity so has received less attention than NK-92. KHYG-1 cells areknown to be pre-activated. Unlike endogenous NK cells, KHYG-1 cells arepolarized at all times, increasing their cytotoxicity and making themquicker to respond to external stimuli. NK-92 cells have a higherbaseline cytotoxicity than KHYG-1 cells.

It is therefore clear that current adoptive immunotherapy protocols areaffected by donor variability in the quantity and quality of effectorcells, variables that could be eliminated if effective cell lines wereavailable to provide more standardized therapy.

A considerable amount of research into NK cell cytotoxicity has beenperformed using mouse models. One example is the finding that perforinand granzyme B mRNA are constitutively transcribed in mouse NK cells,but minimal levels of protein are detected until stimulation oractivation of the NK cells (Fehniger et al, 2007). Although this workand other work using mouse NK cells is of interest, it cannot be reliedupon as conclusive evidence for NK cell cytotoxicity in humans. Incontrast to the above example, human NK cells express high levels ofperforin and granzyme B protein prior to stimulation (Leong et al,2011). The result being that when either mouse or human NK cells arefreshly isolated in culture, the mouse NK cells have weak cytolyticactivity, whereas the human NK cells exhibit strong cytolyticcapabilities.

Mouse and human NK cells also vary greatly in their expression markers,signalling cascades and tissue distribution. For example, CD56 is usedas a marker for human NK cells, whereas mouse NK cells do not expressthis marker at all. Furthermore, a well-established mechanism forregulating NK cell cytotoxicity is via ligand binding NK activation andinhibitory receptors. Two of the most prominent human NK activationreceptors are known to be NKp30 and NKp44, neither of which areexpressed on mouse NK cells. With regards to NK inhibitory receptors,whilst human NK cells express KIRs that recognise MHC class I and dampencytotoxic activity, mouse NK cells do not express KIRs at all but,instead, express Ly49s (Trowsdale et al, 2001). All in all, despitemouse NK cells achieving the same function as human NK cells in theirnatural physiological environment, the mechanisms that fulfil this rolevary significantly between species.

Thus there exists a need for alternative and preferably improved humanNK cells and human NK cell lines, e.g. with a more cytotoxic profile.

-   -   An object of the invention is to provide NK cells and NK cell        lines with a more cytotoxic phenotype. A further object is to        provide methods for producing modified NK cells and NK cell        lines, compositions containing the cells or cell lines and uses        of said compositions in the treatment of cancers. More        particular embodiments aim to provide treatments for identified        cancers, e.g. blood cancers, such as leukemias. Specific        embodiments aim at combining two or more modifications of NK        cells and NK cell lines to further enhance the cytotoxicity of        the modified cells.

SUMMARY OF THE INVENTION

There are provided herein modified NK cells and NK cell lines with amore cytotoxic phenotype, and methods of making the cells and celllines. Also provided are compositions of modified NK cells and NK celllines, and uses of said compositions for treating cancer.

The invention provides methods of modifying NK cells and NK cell linesusing, for example, genetic engineering to knock out genes encodinginhibitory receptors, express genes encoding TRAIL ligands and variants,and express genes encoding chimeric antigen receptors (CARs) and/or Fcreceptors.

Furthermore, compositions of the invention include NK cells and NK celllines in which two or more modifications are provided, wherein multiplemodifications further enhance the cytotoxic activity of the composition.

According to the invention, there are further provided methods oftreating cancer, e.g. blood cancer, using modified NK cell lines, e.g.derivatives of KHYG-1 cells, wherein the modified NK cell lines areengineered to lack expression of checkpoint inhibitory receptors,express TRAIL ligand variants and/or express CARs and/or Fc receptors.

Diseases particularly treatable according to the invention includecancers, blood cancers, leukemias and specifically acute myeloidleukemia. Tumors and cancers in humans in particular can be treated.References to tumors herein include references to neoplasms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the DNA sequence of the LIR2 gene target region and marksthe gRNA flanking regions.

FIG. 2 shows the DNA sequence of the CTLA4 gene target region and marksthe gRNA flanking regions.

FIG. 3 shows the gRNA construct (expression vector) used fortransfection.

FIG. 4 shows gel electrophoresis bands for parental and mutated LIR2DNA, before and after transfection.

FIG. 5 shows gel electrophoresis bands for parental and mutated CTLA4DNA, before and after transfection.

FIG. 6A is a FACS plot showing successful CD96 knockdown usingelectroporation.

FIG. 6B is a FACS plot showing successful CD96 knockdown usingelectroporation.

FIG. 7 is a bar chart showing increased cytotoxicity of CD96 knockdownKHYG-1 cells against K562 cells at various E:T ratios.

FIG. 8 shows knockdown of CD328 (Siglec-7) in NK-92 cells.

FIG. 9 shows enhanced cytotoxicity of NK Cells with the CD328 (Siglec-7)knockdown.

FIG. 10 shows a FACS plot of the baseline expression of TRAIL on KHYG-1cells.

FIG. 11 shows a FACS plot of the expression of TRAIL and TRAIL variantafter transfection of KHYG-1 cells.

FIG. 12 shows a FACS plot of the expression of CD107a after transfectionof KHYG-1 cells;

FIG. 13 shows the effects of transfecting KHYG-1 cells with TRAIL andTRAIL variant on cell viability;

FIG. 14 shows a FACS plot of the baseline expression of DR4, DR5, DcR1and DcR2 on both KHYG-1 cells and NK-92 cells.

FIGS. 15, 16 and 17 show the effects of expressing TRAIL or TRAILvariant in KHYG-1 cells on apoptosis of three target cell populations:K562, RPMI8226 and MM1.S, respectively.

FIG. 18 shows two FACS plots of DR5 expression on RPMI8226 cells andMM1.S cells, respectively, wherein the effects of Bortezomib treatmenton DR5 expression are shown.

FIG. 19 shows FACS plots of apoptosis in Bortezomib-pretreated/untreatedMM1.S cells co-cultured with KHYG-1 cells with/without the TRAILvariant.

FIG. 20 shows a FACS plot of perforin expression levels in KHYG-1 cellstreated with 100 nM CMA for 2 hours;

FIG. 21 shows FACS plots of KHYG-1 cell viability after treatment with100 nM CMA or vehicle.

FIG. 22 shows FACS plots of apoptosis in MM1.S cells co-cultured withKHYG-1 cells with/without the TRAIL variant and pretreated with/withoutCMA.

FIG. 23 shows FACS plots of apoptosis in K562 cells co-cultured withKHYG-1 cells with CD96-siRNA and/or TRAIL variant expression.

FIG. 24 shows FACS plots of apoptosis in MM1.S cells co-cultured withKHYG-1 cells with CD96-siRNA and/or TRAIL variant expression.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, the present invention provides a natural killer (NK) cellor NK cell line that has been genetically modified to increase itscytotoxicity.

As described in detail below in examples, NK cells and NK cell lineshave been genetically modified so as to increase their cytotoxicactivity against cancer.

Together, the NK cells and NK cell lines of the invention will bereferred to as the NK cells (unless the context requires otherwise).

In certain embodiments of the invention NK cells are provided havingreduced or absent checkpoint inhibitory receptor function. Thus inexamples below, NK cells are produced that have one or more checkpointinhibitory receptor genes knocked out. Preferably, these receptors arespecific checkpoint inhibitory receptors. Preferably still, thesecheckpoint inhibitory receptors are one or more or all of CD96(TACTILE), CD152 (CTLA4), CD223 (LAG-3), CD279 (PD-1), CD328 (SIGLEC7),SIGLEC9, TIGIT and/or TIM-3.

In other embodiments, NK cells are provided in which one or moreinhibitory receptor signaling pathways are knocked out or exhibitreduced function—the result again being reduced or absent inhibitoryreceptor function. For example, signaling pathways mediated by SHP-1,SHP-2 and/or SHIP are knocked out by genetic modification of the cells.

The resulting NK cells exhibit improved cytotoxicity and are of greateruse therefore in cancer therapy, especially blood cancer therapy, inparticular treatment of leukemias and multiple myeloma.

In an embodiment, the genetic modification occurs before the cell hasdifferentiated into an NK cell. For example, pluripotent stem cells(e.g. iPSCs) can be genetically modified to lose the capacity to expressone or more checkpoint inhibitory receptors. The modified iPSCs are thendifferentiated to produce genetically modified NK cells with increasedcytotoxicity.

It is preferred to reduce function of checkpoint inhibitory receptorsover other inhibitory receptors, due to the expression of the formerfollowing NK cell activation. The normal or ‘classical’ inhibitoryreceptors, such as the majority of the KIR family, NKG2A and LIR-2, bindMHC class I and are therefore primarily involved in reducing the problemof self-targeting. Preferably, therefore, checkpoint inhibitoryreceptors are knocked out. Reduced or absent function of these receptorsaccording to the invention prevents cancer cells from suppressing immuneeffector function (which might otherwise occur if the receptors werefully functional). Thus a key advantage of these embodiments of theinvention lies in NK cells that are less susceptible to suppression oftheir cytotoxic activities by cancer cells; as a result they are usefulin cancer treatment.

As used herein, references to inhibitory receptors generally refer to areceptor expressed on the plasma membrane of an immune effector cell,e.g. a NK cell, whereupon binding its complementary ligand resultingintracellular signals are responsible for reducing the cytotoxicity ofsaid immune effector cell. These inhibitory receptors are expressedduring both ‘resting’ and ‘activated’ states of the immune effector celland are often associated with providing the immune system with a‘self-tolerance’ mechanism that inhibits cytotoxic responses againstcells and tissues of the body. An example is the inhibitory receptorfamily ‘KIR’ which are expressed on NK cells and recognize MHC class Iexpressed on healthy cells of the body.

Also as used herein, checkpoint inhibitory receptors are usuallyregarded as a subset of the inhibitory receptors above. Unlike otherinhibitory receptors, however, checkpoint inhibitory receptors areexpressed at higher levels during prolonged activation and cytotoxicityof an immune effector cell, e.g. a NK cell. This phenomenon is usefulfor dampening chronic cytotoxicity at, for example, sites ofinflammation. Examples include the checkpoint inhibitory receptors PD-1,CTLA-4 and CD96, all of which are expressed on NK cells.

The invention hence also provides a NK cell lacking a gene encoding acheckpoint inhibitory receptor selected from CD96 (TACTILE), CD152(CTLA4), CD223 (LAG-3), CD279 (PD-1), CD328 (SIGLEC7), SIGLEC9, TIGITand TIM-3.

A NK cell lacking a gene can refer to either a full or partial deletion,mutation or otherwise that results in no functional gene product beingexpressed. In embodiments, the NK cell lacks genes encoding two or moreof the inhibitory receptors.

More specific embodiments comprise a NK cell lacking a gene encoding acheckpoint inhibitory receptor selected from CD96 (TACTILE), CD152(CTLA4) and CD279 (PD-1). Preferred embodiments comprise a NK cell beinga derivative of KHYG-1.

In examples described below, the inventors have reliably shown thecytotoxic effects of using siRNA to knock down expression of thecheckpoint inhibitory receptor CD96 in KHYG-1 cells. CD96 knockdown (KD)KHYG-1 cells demonstrated enhanced cytotoxicity against leukemia cellsat a variety of effector:target (E:T) ratios.

In other embodiments of the invention NK cells are provided that expressa TRAIL ligand or, preferably, a mutant (variant) TRAIL ligand. Asfurther described in examples below, cytotoxicity-enhancingmodifications of NK cells hence also include increased expression ofboth TRAIL ligand and/or mutated TRAIL ligand variants.

The resulting NK cells exhibit increased binding to TRAIL receptors and,as a result, increased cytotoxicity against cancers, especially bloodcancers, in particular leukemias.

The mutants/variants preferably have lower affinity (or in effect noaffinity) for ‘decoy’ receptors, compared with the binding of wild typeTRAIL to decoy receptors. Such decoy receptors represent a class ofTRAIL receptors that bind TRAIL ligand but do not have the capacity toinitiate cell death and, in some cases, act to antagonize the deathsignaling pathway. Mutant/variant TRAIL ligands may be preparedaccording to WO 2009/077857.

The mutants/variants may separately have increased affinity for TRAILreceptors, e.g. DR4 and DR5. Wildtype TRAIL is typically known to have aK_(D) of >2 nM for DR4, >5 nM for DR5 and >20 nM for the decoy receptorDcR1 (WO 2009/077857; measured by surface plasmon resonance), or around50 to 100 nM for DR4, 1 to 10 nM for DR5 and 175 to 225 nM for DcR1(Truneh, A. et al. 2000; measured by isothermal titration calorimetryand ELISA). Therefore, an increased affinity for DR4 is suitably definedas a K_(D) of <2 nM or <50 nM, respectively, whereas an increasedaffinity for DR5 is suitably defined as a K_(D) of <5 nM or <1 nM,respectively. A reduced affinity for decoy receptor DcR1 is suitablydefined as a K_(D) of >50 nM or >225 nM, respectively. In any case, anincrease or decrease in affinity exhibited by the TRAIL variant/mutantis relative to a baseline affinity exhibited by wildtype TRAIL. Theaffinity is preferably increased at least 10%, more preferably at least25%, compared with that exhibited by wildtype TRAIL.

The TRAIL variant preferably has an increased affinity for DR5 ascompared with its affinity for DR4, DcR1 and DcR2. Preferably, theaffinity is at least 1.5-fold, 2-fold, 5-fold, 10-fold, 100-fold, oreven 1,000-fold or greater for DR5 than for one or more of DR4, DcR1 andDcR2. More preferably, the affinity is at least 1.5-fold, 2-fold,5-fold, 10-fold, 100-fold, or even 1,000-fold or greater for DR5 thanfor at least two, and preferably all, of DR4, DcR1 and DcR2.

A key advantage of these embodiments of the invention lies in NK cellsthat have greater potency in killing cancer cells.

Further specific embodiments comprise a NK cell expressing a mutantTRAIL ligand that has reduced or no affinity for TRAIL decoy receptors.Preferably, this NK cell is a derivative of KHYG-1. Further specificembodiments comprise a NK cell expressing a mutant TRAIL ligand that hasreduced or no affinity for TRAIL decoy receptors and increased affinityfor DR4 and/or DR5.

In examples of the invention, described in more detail below, NK cellswere genetically modified to express a mutant TRAIL. Modified KHYG-1cells expressed mutant TRAIL, and NK-92 expressed a mutant TRAIL. Themodified KHYG-1 cells exhibited improved cytotoxicity against cancercell lines in vitro. KHYG-1 cells express TRAIL receptors (e.g. DR4 andDR5), but at low levels. Other preferred embodiments of the modified NKcells express no or substantially no TRAIL receptors, or do so only at alow level—sufficiently low that viability of the modified NK cells isnot adversely affected by expression of the mutant TRAIL.

In an optional embodiment, treatment of a cancer using modified NK cellsexpressing TRAIL or a TRAIL variant is enhanced by administering to apatient an agent capable of upregulating expression of TRAIL deathreceptors on cancer cells. This agent may be administered prior to, incombination with or subsequently to administration of the modified NKcells. It is preferable, however, that the agent is administered priorto administering the modified NK cells.

In a preferred embodiment the agent upregulates expression of DR5 oncancer cells. The agent may optionally be a chemotherapeutic medication,e.g. Bortezomib, and administered in a low dose capable of upregulatingDR5 expression on the cancer.

The invention is not limited to any particular agents capable ofupregulating DR5 expression, but examples of DR5-inducing agents includeBortezomib, Gefitinib, Piperlongumine, Doxorubicin, Alpha-tocopherylsuccinate and HDAC inhibitors.

According to a preferred embodiment of the invention, the mutant/variantTRAIL ligand is linked to one or more NK cell costimulatory domains,e.g. 41BB/CD137, CD3zeta/CD247, DAP12 or DAP10. Binding of the variantto its receptor on a target cell thus promotes apoptotic signals withinthe target cell, as well as stimulating cytotoxic signals in the NKcell.

According to further preferred embodiments of the invention, NK cellsare provided that both have reduced checkpoint inhibitory receptorfunction and also express a mutant TRAIL ligand, as described in moredetail above in relation to these respective NK cell modifications. Ineven more preferred embodiments, a NK cell expressing a mutant TRAILligand that has reduced or no affinity for TRAIL decoy receptors and maybe a derivative of KHYG-1, further lacks a gene encoding a checkpointinhibitory receptor selected from CD96 (TACTILE), CD152 (CTLA4), CD223(LAG-3), CD279 (PD-1), CD328 (SIGLEC7), SIGLEC9, TIGIT and TIM-3.

The present invention also provides NK cells and NK cell lines,preferably KHYG-1 cells and derivatives thereof, modified to express oneor more CARs.

Suitably for cancer therapy uses, the CARs specifically bind to one ormore ligands on cancer cells, e.g. CS1 (SLAMF7) on myeloma cells. Foruse in treating specific cancers, e.g. multiple myeloma, the CAR maybind CD38. For example, the CAR may include the binding properties ofe.g. variable regions derived from, similar to, or identical with thosefrom the known monoclonal antibody daratumumab. Such NK cells may beused in cancer therapy in combination with an agent that inhibitsangiogenesis, e.g. lenalidomide. For use in therapy of cancers,especially leukemias and AML in particular, the CAR may bind to CLL-1.

The CAR-NKs may be bispecific, wherein their affinity is for twodistinct ligands/antigens. Bispecific CAR-NKs can be used either forincreasing the number of potential binding sites on cancer cells or,alternatively, for localizing cancer cells to other immune effectorcells which express ligands specific to the NK-CAR. For use in cancertherapy, a bispecific CAR may bind to a target tumor cell and to aneffector cell, e.g. a T cell, NK cell or macrophage. Thus, for example,in the case of multiple myeloma, a bispecific CAR may bind a T cellantigen (e.g. CD3, etc.) and a tumor cell marker (e.g. CD38, etc.). Abispecific CAR may alternatively bind to two separate tumor cellmarkers, increasing the overall binding affinity of the NK cell for thetarget tumor cell. This may reduce the risk of cancer cells developingresistance by downregulating one of the target antigens. An example inthis case, in multiple myeloma, would be a CAR binding to both CD38 andCS-1/SLAMF7. Another tumor cell marker suitably targeted by the CAR is a“don't eat me” type marker on tumors, exemplified by CD47.

Optional features of the invention include providing furthermodifications to the NK cells and NK cell lines described above,wherein, for example, a Fc receptor (which can be CD16, CD32 or CD64,including subtypes and derivatives) is expressed on the surface of thecell. In use, these cells can show increased recognition ofantibody-coated cancer cells and improve activation of the cytotoxicresponse.

Further optional features of the invention include adapting the modifiedNK cells and NK cell lines to better home to specific target regions ofthe body. NK cells of the invention may be targeted to specific cancercell locations. In preferred embodiments for treatment of blood cancers,NK effectors of the invention are adapted to home to bone marrow.Specific NK cells are modified by fucosylation and/or sialylation tohome to bone marrow. This may be achieved by genetically modifying theNK cells to express the appropriate fucosyltransferase and/orsialyltransferase, respectively. Increased homing of NK effector cellsto tumor sites may also be made possible by disruption of the tumorvasculature, e.g. by metronomic chemotherapy, or by using drugstargeting angiogenesis (Melero et al, 2014) to normalize NK cellinfiltration via cancer blood vessels.

Yet another optional feature of the invention is to provide modified NKcells and NK cell lines with an increased intrinsic capacity for rapidgrowth and proliferation in culture. This can be achieved, for example,by transfecting the cells to overexpress growth-inducing cytokines IL-2and IL-15. Moreover, this optional alteration provides a cost-effectivealternative to replenishing the growth medium with cytokines on acontinuous basis.

The invention further provides a method of making a modified NK cell orNK cell line, comprising genetically modifying the cell or cell line asdescribed herein so as to increase its cytotoxicity. This geneticmodification can be a stable knockout of a gene, e.g. by CRISPR, or atransient knockdown of a gene, e.g. by siRNA.

In a preferred embodiment, a stable genetic modification technique isused, e.g. CRISPR, in order to provide a new NK cell line with increasedcytotoxicity, e.g. a derivative of KHYG-1 cells.

In embodiments, the method is for making a NK cell or NK cell line thathas been modified so as to reduce inhibitory receptor function.Preferably, these inhibitory receptors are checkpoint inhibitoryreceptors.

More specific embodiments comprise a method for making a NK cell or NKcell line with reduced inhibitory receptor function, wherein thecheckpoint inhibitory receptors are selected from CD96 (TACTILE), CD152(CTLA4), CD223 (LAG-3), CD279 (PD-1), CD328 (SIGLEC7), SIGLEC9, TIGITand TIM-3.

In preferred embodiments, the method comprises modifying the NK cells toreduce function of two or more of the inhibitory receptors.

The invention still further provides a method of making a modified NKcell or NK cell line comprising genetically modifying the cell or cellline to express TRAIL ligand or mutant TRAIL (variant) ligand.

In embodiments, the method comprises modifying a NK cell or NK cell lineto express mutant TRAIL ligand that has an increased affinity for TRAILreceptors. Preferably, the TRAIL receptors are DR4 and/or DR5. Preferredembodiments provide a method of modifying the NK cells or NK cell linesto express a mutant TRAIL ligand that has a reduced affinity for decoyTRAIL receptors.

In further preferred embodiments, the method comprises modifying a NKcell or NK cell line to remove function of a checkpoint inhibitoryreceptor and also to express a mutant TRAIL ligand with reduced or nobinding affinity for decoy TRAIL receptors.

Further typical embodiments provide a method for making a NK cell or NKcell line, in which function of one or more checkpoint inhibitoryreceptors has been removed and/or a mutant TRAIL ligand is expressed,which has reduced or no binding affinity for decoy TRAIL receptors, andthe cell is further modified to express a CAR or bispecific CAR. Theproperties of the CAR are optionally as described above.

In embodiments, the method comprises making a NK cell or NK cell line,in which function of one or more checkpoint inhibitory receptors hasbeen removed and/or a mutant TRAIL ligand is expressed, which hasreduced or no binding affinity for decoy TRAIL receptors, and the cellis optionally modified to express a CAR or bispecific CAR, and the cellis further modified to express one or more Fc receptors. Suitable Fcreceptors are selected from CD16 (FcRIII), CD32 (FcRII) and CD64 (FcRI).

Preferred embodiments of all the above comprise a method of making NKcells and NK cell lines being a derivative of KHYG-1.

As per the objects of the invention, the modified NK cell, NK cell lineor composition thereof with increased cytotoxicity are for use intreating cancer in a patient, especially blood cancer.

In preferred embodiments, the modified NK cell, NK cell line orcomposition is for use in treating blood cancers including acutelymphocytic leukemia (ALL), acute myeloid leukemia (AML), chroniclymphocytic leukemia (CLL), chronic myeloid leukemia (CML), Hodgkin'slymphoma, non-Hodgkin's lymphoma, including T-cell lymphomas and B-celllymphomas, asymptomatic myeloma, smoldering multiple myeloma (SMM),active myeloma or light chain myeloma.

In even more preferred embodiments, the invention is a NK cell lineobtained as a derivative of KYHG-1 by reducing checkpoint inhibitoryreceptor function in a KHYG-1 cell or expressing a mutant TRAIL ligandin a KHYG-1 cell, or both, for use in treating blood cancer.

Modified NK cells, NK cell lines and compositions thereof describedherein, above and below, are suitable for treatment of cancer, inparticular cancer in humans, e.g. for treatment of cancers of bloodcells or solid cancers. The NK cells and derivatives are preferablyhuman NK cells. For human therapy, human NK cells are preferably used.

Various routes of administration will be known to the skilled person todeliver active agents and combinations thereof to a patient in need.Embodiments of the invention are for blood cancer treatment.Administration of the modified NK cells and/or NK cell lines can besystemic or localized, such as for example via the intraperitonealroute.

In other embodiments, active agent is administered more directly. Thusadministration can be directly intratumoral, suitable especially forsolid tumors.

NK cells in general are believed suitable for the methods, uses andcompositions of the invention. As per cells used in certain examplesherein, the NK cell can be a NK cell obtained from a cancer cell line.Advantageously, a NK cell, preferably treated to reduce itstumorigenicity, for example by rendering it mortal and/or incapable ofdividing, can be obtained from a blood cancer cell line and used inmethods of the invention to treat blood cancer.

To render a cancer-derived cell more acceptable for therapeutic use, itis generally treated or pre-treated in some way to reduce or remove itspropensity to form tumors in the patient. Specific modified NK celllines used in examples are safe because they have been renderedincapable of division; they are irradiated and retain their killingability but die within about 3-4 days. Specific cells and cell lines arehence incapable of proliferation, e.g. as a result of irradiation.Treatments of potential NK cells for use in the methods herein includeirradiation to prevent them from dividing and forming a tumor in vivoand genetic modification to reduce tumorigenicity, e.g. to insert asequence encoding a suicide gene that can be activated to prevent thecells from dividing and forming a tumor in vivo. Suicide genes can beturned on by exogenous, e.g. circulating, agents that then cause celldeath in those cells expressing the gene. A further alternative is theuse of monoclonal antibodies targeting specific NK cells of the therapy.CD52, for example, is expressed on KHYG-1 cells and binding ofmonoclonal antibodies to this marker can result in antibody-dependentcell-mediated cytotoxicity (ADCC) and KHYG-1 cell death.

As discussed in an article published by Suck et al, 2006, cancer-derivedNK cells and cell lines are easily irradiated using irradiators such asthe Gammacell 3000 Elan. A source of Cesium-137 is used to control thedosing of radiation and a dose-response curve between, for example, 1 Gyand 50 Gy can be used to determine the optimal dose for eliminating theproliferative capacity of the cells, whilst maintaining the benefits ofincreased cytotoxicity. This is achieved by assaying the cells forcytotoxicity after each dose of radiation has been administered.

There are significant benefits of using an irradiated NK cell line foradoptive cellular immunotherapy over the well-established autologous orMHC-matched T cell approach. Firstly, the use of a NK cell line with ahighly proliferative nature means expansion of modified NK cell linescan be achieved more easily and on a commercial level. Irradiation ofthe modified NK cell line can then be carried out prior toadministration of the cells to the patient. These irradiated cells,which retain their useful cytotoxicity, have a limited life span and,unlike modified T cells, will not circulate for long periods of timecausing persistent side-effects.

Additionally, the use of allogeneic modified NK cells and NK cell linesmeans that MHC class I expressing cells in the patient are unable toinhibit NK cytotoxic responses in the same way as they can to autologousNK cytotoxic responses. The use of allogeneic NK cells and cell linesfor cancer cell killing benefits from the previously mentioned GVLeffect and, unlike for T cells, allogeneic NK cells and cell lines donot stimulate the onset of GVHD, making them a much preferred option forthe treatment of cancer via adoptive cellular immunotherapy.

As set out in the claims and elsewhere herein, the invention providesthe following embodiments:

1. A natural killer (NK) cell or NK cell line that has been geneticallymodified to increase its cytotoxicity.

2. A NK cell or NK cell line according to embodiment 1, modified to havereduced function of one or more inhibitory receptors.

3. A NK cell or NK cell line according to embodiment 2, wherein theinhibitory receptors are checkpoint inhibitory receptors.

4. A NK cell or NK cell line according to embodiment 3, wherein thecheckpoint inhibitory receptors are selected from CD96 (TACTILE), CD152(CTLA4), CD223 (LAG-3), CD279 (PD-1), CD328 (SIGLEC7), SIGLEC9, TIGITand TIM-3.

5. A NK cell or NK cell line according to any of embodiments 2 to 4,modified to have reduced function of two or more inhibitory receptors.

6. A NK cell or NK cell line according to any of embodiments 1 to 5,modified to express TRAIL ligand.

7. A NK cell or NK cell line according to embodiment 6, wherein theTRAIL ligand is a mutant TRAIL ligand.

8. A NK cell or NK cell line according to embodiment 7, wherein themutant TRAIL ligand has an increased affinity for TRAIL receptors, e.g.DR4 and/or DR5.

9. A NK cell or NK cell line according to any of embodiments 7 to 8,wherein the mutant TRAIL ligand has reduced affinity for decoy TRAILreceptors.

10. A NK cell or NK cell line according to any preceding embodiment,modified to remove function of a checkpoint inhibitory receptor and alsomodified to express a mutant TRAIL ligand with reduced or no bindingaffinity for decoy TRAIL receptors.

11. A NK cell or NK cell line according to any preceding embodiment,expressing a chimeric antigen receptor (CAR).

12. A NK cell or NK cell line according to embodiment 11, wherein theCAR is a bispecific CAR.

13. A NK cell or NK cell line according to embodiment 12, wherein thebispecific CAR binds two ligands on one cell type.

14. A NK cell or NK cell line according to embodiment 12, wherein thebispecific CAR binds one ligand on each of two distinct cell types.

15. A NK cell or NK cell line according to embodiments 11 and 12,wherein the ligand(s) for the CAR or bispecific CAR are expressed on acancer cell.

16. A NK cell or NK cell line according to embodiment 13, wherein theligands for the bispecific CAR are both expressed on a cancer cell.

17. A NK cell or NK cell line according to embodiment 14, wherein theligands for the bispecific CAR are expressed on a cancer cell and animmune effector cell.

18. A NK cell or NK cell line according to any preceding embodiment,modified to express one or more Fc receptors.

19. A NK cell or NK cell line according to embodiment 18, wherein the Fcreceptors are selected from CD16 (FcRIII), CD32 (FcRII) and CD64 (FcRI).

20. A NK cell or NK cell line according to any preceding embodiment,wherein the cell line is a derivative of the KHYG-1 cell line.

21. A NK cell lacking a gene encoding a checkpoint inhibitory receptorselected from CD96 (TACTILE), CD152 (CTLA4), CD223 (LAG-3), CD279(PD-1), CD328 (SIGLEC7), SIGLEC9, TIGIT and TIM-3.

22. A NK cell according to embodiment 21, lacking genes encoding two ormore checkpoint inhibitory receptors selected from CD96 (TACTILE), CD152(CTLA4), CD223 (LAG-3), CD279 (PD-1), CD328 (SIGLEC7), SIGLEC9, TIGITand TIM-3.

23. A NK cell according to embodiment 21 or 22, wherein the checkpointinhibitory receptor is selected from CD96 (TACTILE), CD152 (CTLA4) andCD279 (PD-1).

24. A NK cell according to any of embodiments 21 to 23, being aderivative of KHYG-1.

25. A NK cell expressing a mutant TRAIL ligand that has reduced or noaffinity for TRAIL decoy receptors.

26. A NK cell according to embodiment 25, being a derivative of KHYG-1.

27. A NK cell according to embodiment 25 or 26, lacking a gene encodinga checkpoint inhibitory receptor selected from CD96 (TACTILE), CD152(CTLA4), CD223 (LAG-3), CD279 (PD-1), CD328 (SIGLEC7), SIGLEC9, TIGITand TIM-3.

28. A NK cell or cell line according to any preceding embodiment,incapable of proliferation, e.g. as a result of irradiation.

29. A method of making a modified NK cell or NK cell line, comprisinggenetically modifying the cell or cell line so as to increase itscytotoxicity.

30. A method according to embodiment 29, wherein the NK cell or NK cellline is modified so as to reduce inhibitory receptor function.

31. A method according to embodiment 30, wherein the inhibitoryreceptors are checkpoint inhibitory receptors.

32. A method according to embodiment 31, wherein the checkpointinhibitory receptors are selected from CD96 (TACTILE), CD152 (CTLA4),CD223 (LAG-3), CD279 (PD-1), CD328 (SIGLEC7), SIGLEC9, TIGIT and TIM-3.

33. A method according to any of embodiments 29 to 32, comprisingmodifying the NK cells to reduce function of two or more of theinhibitory receptors.

34. A method according to any of embodiments 29 to 33, comprisingmodifying the NK cell or NK cell line to express TRAIL ligand or mutantTRAIL ligand.

35. A method according to embodiment 34, wherein the mutant TRAIL ligandhas an increased affinity for TRAIL receptors.

36. A method according to embodiment 35, wherein the TRAIL receptors areDR4 and/or DR5.

37. A method according to any of embodiments 34 to 36, wherein themutant TRAIL ligand has a reduced affinity for decoy TRAIL receptors.

38. A method according to any of embodiments 29 to 37, wherein the NKcell or NK cell line is modified to remove function of a checkpointinhibitory receptor and also modified to express a mutant TRAIL ligandwith reduced or no binding affinity for decoy TRAIL receptors.

39. A method according to embodiment 38, wherein the NK cell or NK cellline is modified to express a CAR or bispecific CAR.

40. A method according to embodiment 39, wherein the bispecific CARbinds two ligands on one cell type.

41. A method according to embodiment 39, wherein the bispecific CARbinds one ligand on each of two distinct cell types.

42. A method according to embodiment 39, wherein the ligand(s) for theCAR or bispecific CAR are expressed on a cancer cell.

43. A method according to embodiment 40, wherein the ligands for thebispecific CAR are both expressed on a cancer cell.

44. A method according to embodiment 41, wherein the ligands for thebispecific CAR are expressed on a cancer cell and an immune effectorcell.

45. A method according to any of embodiments 29 to 44, wherein the NKcell or NK cell line is modified to express one or more Fc receptors.

46. A method according to embodiment 45, wherein the Fc receptors areselected from CD16 (FcRIII), CD32 (FcRII) and CD64 (FcRI).

47. A method according to any of embodiments 29 to 46, wherein the cellline is a derivative of the KHYG-1 cell line.

48. A NK cell or NK cell line obtained by a method according to any ofembodiments 29 to 47.

49. A KHYG-1 derivative obtained by a method according to any ofembodiments 29 to 48.

50. A modified NK cell, NK cell line or composition thereof withincreased cytotoxicity for use in treating cancer in a patient.

51. A NK cell or NK cell line according to any of embodiments 1 to 28,or obtained according to any of embodiments 29 to 49, for use accordingto embodiment 50.

52. A modified NK cell, NK cell line or composition for use according toembodiment 50 or 51, wherein the cancer is a blood cancer.

53. A modified NK cell, NK cell line or composition for use according toembodiment 52, wherein the blood cancer is acute lymphocytic leukemia(ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL),chronic myeloid leukemia (CML), Hodgkin's lymphoma, non-Hodgkin'slymphoma, including T-cell lymphomas and B-cell lymphomas, asymptomaticmyeloma, smoldering multiple myeloma (SMM), active myeloma or lightchain myeloma.

54. A NK cell line obtained as a derivative of KYHG-1 by reducingcheckpoint inhibitory receptor function in a KHYG-1 cell or expressing amutant TRAIL ligand in a KHYG-1 cell, or both, for use in treating bloodcancer.

EXAMPLES

The present invention is now described in more and specific details inrelation to the production of NK cell line KHYG-1 derivatives, modifiedto exhibit more cytotoxic activity and hence ability to cause leukemiacell death in humans.

The invention is now illustrated in specific embodiments with referenceto the accompanying drawings in which:

DNA, RNA and amino acid sequences are referred to below, in which:

SEQ ID NO: 1 is the full LIR2 DNA sequence;

SEQ ID NO: 2 is the LIR2 amino acid sequence;

SEQ ID NO: 3 is the LIR2 g9 gRNA sequence;

SEQ ID NO: 4 is the LIR2 g18 gRNA sequence;

SEQ ID NO: 5 is the LIR2 forward primer sequence;

SEQ ID NO: 6 is the LIR2 reverse primer sequence;

SEQ ID NO: 7 is the full CTLA4 DNA sequence;

SEQ ID NO: 8 is the CTLA4 amino acid sequence;

SEQ ID NO: 9 is the CTLA4 g7 gRNA sequence;

SEQ ID NO: 10 is the CTLA4 g15 gRNA sequence;

SEQ ID NO: 11 is the CTLA4 forward primer sequence; and

SEQ ID NO: 12 is the CTLA4 reverse primer sequence.

Example 1—Knockout of Inhibitory Receptor Function

CRISPR/Cas9

Cells were prepared as follows, having inhibitory receptor functionremoved. gRNA constructs were designed and prepared to target genesencoding the ‘classical’ inhibitory receptor LIR2 and the ‘checkpoint’inhibitory receptor CTLA4 in the human genome of NK cells. CRISPR/Cas9genome editing was then used to knock out the LIR2 and CTLA4 targetgenes.

Two gRNA candidates were selected for each target gene and theircleavage efficacies in K562 cells determined. The sequences of the gRNAcandidates are shown in Table 1 and the Protospacer Adjacent Motif (PAM)relates to the last 3 bases of the sequence. The flanking regions of thegRNA sequences on the LIR2 gene (SEQ ID NO: 1) and the CTLA4 gene (SEQID NO: 7) are shown in FIGS. 1 and 2, respectively.

TABLE 1 gRNA candidates and sequences Gene Plasmid Name Sequence hLIR2SM682.LIR2.g9 GAGTCACAGGTGGCATTTGGCGG (SEQ ID NO: 3) SM682.LIR2.g18CGAATCGCAGGTGGTCGCACAGG (SEQ ID NO: 4) hCTLA4 SM683.CTLA4.g7CACTCACCTTTGCAGAAGACAGG (SEQ ID NO: 9) SM683.CTLA4.g15CCTTGTGCCGCTGAAATCCAAGG (SEQ ID NO: 10)

K562 cells were transfected with the prepared gRNA constructs (FIG. 3)and subsequently harvested for PCR amplification. The presence of GFPexpression was used to report successful incorporation of the gRNAconstruct into the K562 cells. This confirmed expression of the Cas9gene and therefore the ability to knock out expression of the LIR2 andCTLA4 genes.

The cleavage activity of the gRNA constructs was determined using an invitro mismatch detection assay. T7E1 endonuclease I recognises andcleaves non-perfectly matched DNA, allowing the parental LIR2 and CTLA4genes to be compared to the mutated genes following CRISPR/Cas9transfection and non-homologous end joining (NHEJ).

FIG. 4 shows the resulting bands following agarose gel electrophoresisafter knockout of the LIR2 gene with the g9 and g18 gRNA sequences. Thethree bands corresponding to each mutation relate to the parental geneand the two resulting strands following detection of a mismatch in theDNA sequence after transfection. The g9 gRNA sequence resulted in an 11%success rate of transfection, whereas the g18 gRNA resulted in 10%.

FIG. 5 shows the resulting bands following agarose gel electrophoresisafter knockout of the CTLA4 gene with the g7 and g15 gRNA sequences. Theg7 gRNA sequence resulted in a 32% success rate of transfection, whereasthe g15 gRNA resulted in 26%.

Following the successful knockout of LIR2 and CTLA4 in K562 cells,KHYG-1 cells were transfected with gRNA constructs.

KHYG-1 derivative clones having homozygous deletions were selected. ACas9/puromycin acetyltransferase (PAC) expression vector was used forthis purpose. Successfully transfected cells were selected, based ontheir resistance to the antibiotic puromycin.

Cas9 RNP

Another protocol used for knockout of checkpoint inhibitory receptors inNK cells was that of Cas9 RNP transfection. An advantage of using thisprotocol was that similar transfection efficiencies were achievable butwith significantly lower toxicity compared to using the DNA plasmids ofthe CRISPR/Cas9 protocol.

1×10⁶ KHYG1 cells were harvested for each transfection experiment. Thecells were washed with PBS and spun down in a centrifuge. Thesupernatant was then discarded. The CRISPR RNP (RNA binding protein)materials were then prepared as follows:

(1) a 20 μM solution of the required synthesized crRNA and tRNA(purchased from Dharmacon) was prepared.

(2) 4 μl of crRNA (20 μM) and 4 μl of tRNA (20 μM) were mixed together.

(3) The mixture was then added to 2 μl Cas9 protein (5 μg/μl).

(4) All of the components were mixed and incubated at room temperaturefor 10 minutes.

Following the Neon® Transfection System, the cells were mixed with Cas9RNP and electroporation was performed using the following parameters:

Voltage: 1450v

Pulse width: 30 ms

Pulse number: 1

The cells were then transferred to one well of a 12-well platecontaining growth medium (inc. IL-2 and IL-15).

The cells were harvested after 48-72 hours to confirm gene editingefficiency by T7 endonuclease assay and/or Sanger sequencing. Thepresence of indels were confirmed, indicating successful knockout ofCTLA4, PD1 and CD96 in KHYG1 cells.

Site-Specific Nucleases

Another protocol used for knockout of checkpoint inhibitory receptors inNK cells was that of XTN TALEN transfection. An advantage of using thisprotocol was that a particularly high level of specificity wasachievable compared to wildtype CRISPR.

Step 1: Preparation of Reagents

KHYG-1 cells were assayed for certain attributes including transfectionefficiency, single cell cloning efficiency and karyotype/copy number.The cells were then cultured in accordance with the supplier'srecommendations.

Depending on the checkpoint inhibitory receptor being knockout out,nucleases were prepared by custom-design of at least 2 pairs of XTNTALENs. The step of custom-design includes evaluation of gene locus,copy number and functional assessment (i.e. homologs, off-targetevaluation).

Step 2: Cell Line Engineering

The cells were transfected with the nucleases of Step 1; this step wasrepeated up to 3 times in order to obtain high levels of cutting andcultures were split and intermediate cultures maintained prior to eachtransfection.

Initial screening occurred several days after each transfection; thepools of cells were tested for cutting efficiency via the Cel-1 assay.Following the level of cutting reaching acceptable levels or plateausafter repeated transfections, the cells were deemed ready for singlecell cloning.

The pooled cells were sorted to one cell per well in a 96-well plate;the number of plates for each pool was dependent on the single cellcloning efficiency determined in Step 1. Plates were left to incubatefor 3-4 weeks.

Step 3—Screening and Expansion

Once the cells were confluent in the 96-well plates, cultures wereconsolidated and split into triplicate 96-well plates; one plate wasfrozen as a backup, one plate was re-plated to continue the expansion ofthe clones and the final plate was used for genotype confirmation.

Each clone in the genotype plate was analyzed for loss of qPCR signal,indicating all alleles had been modified. Negative clones were PCRamplified and cloned to determine the nature of the indels and lack ofany wildtype or in-frame indels.

Clones with the confirmed knockout were consolidated into no more thanone 24-well plate and further expanded; typically 5-10 frozen cryovialscontaining 1×10⁶ cells per vial for up to 5 individual clones wereproduced per knockout.

Step 4—Validation

Cells were banked under aseptic conditions.

Basic release criteria for all banked cells included viable cell number(pre-freeze and post-thaw), confirmation of identity via STR, basicsterility assurance and mycoplasma testing; other release criteria wereapplied when necessary (karyotype, surface marker expression, high levelsterility, knockout evaluation of transcript or protein, etc).

Example 2—Knockdown of Checkpoint Inhibitory Receptor CD96 Function ViaRNAi

siRNA knockdown of CD96 in KHYG-1 cells was performed byelectroporation. The Nucleofection Kit T was used, in conjunction withthe Amaxa Nucleofector II, from Lonza, as it is appropriate for use withcell lines and can successfully transfect both dividing and non-dividingcells and achieves transfection efficiencies of up to 90%.

Control siRNA (catalog number: sc-37007) and CD96 siRNA (catalog number:sc-45460) were obtained from Santa Cruz Biotechnology. Antibiotic-freeRPMI-1640 containing 10% FBS, 2 mM L-glutamine was used forpost-Nucleofection culture. Mouse anti-human CD96-APC (catalog number:338409) was obtained from Biolegend for staining.

A 20 μM of siRNA stock solution was prepared. The lyophilized siRNAduplex was resuspended in 33 μl of the RNAse-free water (siRNA dilutionbuffer: sc-29527) to FITC-control/control-siRNA, in 165 μl of theRNAse-free water for the target gene siRNA (siRNA CD96).

The tube was heated to 90° C. for 1 minute and then incubated at 37° C.for 60 minutes. The siRNA stock was then stored at −20° C. until needed.

The KHYG-1 cells were passaged one to two days before Nucleofection, asthe cells must be in logarithmic growth phase.

The Nucleofector solution was warmed to room temperature (100 ul persample).

An aliquot of culture medium containing serum and supplements was alsopre-warmed at 37° C. in a 50 ml tube. 6-well plates were prepared byadding 1.5 ml of culture medium containing serum and supplements. Theplates were pre-incubated in a humidified 37° C./5% CO₂ incubator.

2×10⁶ cells in 100 μl Nucleofection solution was mixed gently with 4 μl20 μM siRNA solution (1.5 μg siRNA). Air bubbles were avoided duringmixing. The mixture was transferred into Amaxa certified cuvettes andplaced into the Nucleofector cuvette holder and program U-001 selected.

The program was allowed to finish, and the samples in the cuvettes wereremoved immediately. 500 μl pre-equilibrated culture medium was thenadded to each cuvette. The sample in each cuvette was then gentlytransferred to a corresponding well of the prepared 6-well plate, inorder to establish a final volume of 2 ml per well.

The cells were then incubated in a humidified 37° C./5% CO₂ incubatoruntil transfection analysis was performed. Flow cytometry analysis wasperformed 16-24 hours after electroporation, in order to measure CD96expression levels. This electroporation protocol was carried outmultiple times and found to reliably result in CD96 knockdown in KHYG-1cells (see e.g. FIGS. 6A and 6B).

Example 3—Enhanced Cytotoxicity of NK Cells with a CD96 Knockdown

KHYG-1 cells with and without the CD96 knockdown were co-cultured withK562 cells at different effector:target (E:T) ratios.

Cytotoxicity was measured 4 hours after co-culture, using the DELFIAEuTDA Cytotoxicity Kit from PerkinElmer (Catalog number: AD0116).

Target cells K562 were cultivated in RPMI-1640 medium containing 10%FBS, 2 mM L-glutamine and antibiotics. 96-well V-bottom plates (catalognumber: 83.3926) were bought from SARSTEDT. An Eppendorf centrifuge5810R (with plate rotor) was used to spin down the plate. A VARIOSKANFLASH (with ScanIt software 2.4.3) was used to measure the fluorescencesignal produced by lysed K562 cells.

K562 cells were washed with culture medium and the number of cellsadjusted to 1×10⁶ cells/mL with culture medium. 2-4 mL of cells wasadded to 5 μl of BATDA reagent and incubated for 10 minutes at 37° C.Within the cell, the ester bonds are hydrolysed to form a hydrophilicligand, which no longer passes through the membrane. The cells werecentrifuged at 1500 RPM for 5 mins to wash the loaded K562 cells. Thiswas repeated 3-5 times with medium containing 1 mM Probenecid (SigmaP8761). After the final wash the cell pellet was resuspended in culturemedium and adjusted to about 5×10⁴ cells/mL.

Wells were set up for detection of background, spontaneous release andmaximum release. 100 μL of loaded target cells (5,000 cells) weretransferred to wells in a V-bottom plate and 100 μL of effector cells(KHYG-1 cells) were added at varying cell concentrations, in order toproduce effector to target ratios ranging from 1:1 to 20:1. The platewas centrifuged at 100×g for 1 minute and incubated for 4 hours in ahumidified 5% CO₂ atmosphere at 37° C. For maximum release wells 10 μLof lysis buffer was added to each well 15 minutes before harvesting themedium. The plate was centrifuged at 500×g for 5 minutes.

20 μL of supernatant was transferred to a flat-bottom 96 well plate 200μL of pre-warmed Europium solution added. This was incubated at roomtemperature for 15 mins using a plate shaker. As K562 cells are lysed bythe KHYG-1 cells, they release ligand into the medium. This ligand thenreacts with the Europium solution to form a fluorescent chelate thatdirectly correlates with the amount of lysed cells.

The fluorescence was then measured in a time-resolved fluorometer byusing VARIOSKAN FLASH. The specific release was calculated using thefollowing formula:% specific release=Experiment release−Spontaneous release/Maximumrelease−Spontaneous release

Statistical analysis was performed using Graphpad Prism 6.04 software. Apaired t test was used to compare the difference between siRNA CD96knockdown KHYG-1 cells and control groups (n=3).

The specific release was found to be significantly increased inco-cultures containing the CD96 knockdown KHYG-1 cells. This was thecase at all E:T ratios (see FIG. 7).

As fluorescence directly correlates with cell lysis, it was confirmedthat knocking down CD96 expression in KHYG-1 cells resulted in anincrease in their ability to kill K562 cancer target cells.

Example 4—Enhanced Cytotoxicity of NK Cells with a CD328 (Siglec-7)Knockdown

SiRNA-Mediated Knock-Down of CD328 in NK-92 Cells

Materials, Reagents and Instruments

Control siRNA (catalog number: sc-37007) and CD328 siRNA (catalognumber: sc-106757) were bought from Santa Cruz Biotechnology. To achievetransfection efficiencies of up to 90% with high cell viability (>75%)in NK-92 cells with the Nucleofector™ Device (Nucleofector II, Lonza), aNucleofector™ Kit T from Lonza was used. RPMI-1640 containing 10% FBS, 2mM L-glutamine, antibiotics free, was used for post-Nucleofectionculture. Mouse anti-human CD328-APC (catalog number: 339206) was boughtfrom Biolegend.

Protocol

To make 10 μM of siRNA stock solution

Resuspend lyophilized siRNA duplex in 66 μl of the RNAse-free water(siRNA dilution buffer: sc-29527) to FITC-control/control-siRNA, in 330μl of the RNAse-free water for the target gene siRNA (siRNA CD328).

Heat the tube to 90° C. for 1 minute.

Incubate at 37° C. for 60 minutes.

Store siRNA stock at −20° C. if not used directly.

One Nucleofection sample contains (for 100 μl standard cuvette)

Cell number: 2×10⁶ cells

siRNA: 4 μl of 10 μM stock

Nucleofector solution: 100 μl

Nucleofection

Cultivate the required number of cells. (Passage one or two day beforeNucleofection, cells must be in logarithmic growth phase).

Prepare siRNA for each sample.

Pre-warm the Nucleofector solution to room temperature (100 μl persample).

Pre-warm an aliquot of culture medium containing serum and supplementsat 37° C. in a 50 ml tube. Prepare 6-well plates by filling with 1.5 mlof culture medium containing serum and supplements and pre-incubateplates in a humidified 37° C./5% CO2 incubator.

Take an aliquot of cell culture and count the cells to determine thecell density.

Centrifuge the required number of cells at 1500 rpm for 5 min. Discardsupernatant completely so that no residual medium covers the cellpellet.

Resuspend the cell pellet in room temperature Nucleofector Solution to afinal concentration of 2×10⁶ cells/100 μl. Avoid storing the cellsuspension longer than 15-20 min in Nucleofector Solution, as thisreduces cell viability and gene transfer efficiency.

Mix 100 μl of cell suspension with siRNA.

Transfer the sample into an amaxa certified cuvette. Make sure that thesample covers the bottom of the cuvette, avoid air bubbles whilepipetting. Close the cuvette with the blue cap.

Select the appropriate Nucleofector program (A-024 for NK-92 cells).Insert the cuvette into the cuvette holder (Nucleofector II: rotate thecarousel clockwise to the final position) and press the “x” button tostart the program.

To avoid damage to the cells, remove the samples from the cuvetteimmediately after the program has finished (display showing “OK”). Add500 μl of the pre-warmed culture medium into the cuvette and transferthe sample into the prepared 6-well plate.

Incubate cells in a humidified 37° C./5% CO₂ incubator. Perform flowcytometric analysis and cytotoxicity assay after 16-24 hours.

Results: we followed the above protocol and performed flow cytometryanalysis of CD328 expression level in NK-92 cells. The results of onerepresentative experiment is shown in FIG. 8, confirming successfulknockdown.

Knocking Down CD328 Enhances Cytotoxicity

Materials, Reagents and Instruments

DELFIA EuTDA cytotoxicity kit based on fluorescence enhancing ligand(Catalog number: AD0116) was bought from PerkinElmer. Target cells K562were cultivated in RPMI-1640 medium containing 10% FBS, 2 mM L-glutamineand antibiotics. 96-well V-bottom plates (catalog number: 83.3926) werebought from SARSTEDT. Eppendrof centrifuge 5810R (with plate rotor) wasused to spin down the plate. VARIOSKAN FLASH (with ScanIt software2.4.3) was used to measure the fluorescence signal produced by lysedK562 cells.

Protocol

Load target K562 cells with the fluorescence enhancing ligand DELFIABATDA reagent

Wash K562 cells with medium, adjust the number of cells to 1×10⁶cells/mL with culture medium. Add 2-4 mL of cells to 5 μl of BATDAreagent, incubate for 10 minutes at 37° C.

Spin down at 1500 RPM for 5 minutes to wash the loaded K562 cells for3-5 times with medium containing 1 mM Probenecid (Sigma P8761).

After the final wash resuspend the cell pellet in culture medium andadjust to about 5×10⁴ cells/mL.

Cytotoxicity Assay

Set up wells for detection of background, spontaneously release andmaximum release.

Pipette 100 μL of loaded target cells (5,000 cells) to a V-bottom plate.

Add 100 μL of effector cells (NK-92) of varying cell concentrations.Effector to target ratio ranges from 1:1 to 20:1.

Spin down the plate at 100×g of RCF for 1 minute.

Incubate for 2 hours in a humidified 5% CO2 atmosphere at 37° C. Formaximum release wells, add 10 μL of lysis buffer to each well 15 minutesbefore harvesting the medium.

Spin down the plate at 500×g for 5 minutes.

Transfer 20 μL of supernatant to a flat-bottom 96 well plate, add 200 μLof pre-warmed Europium solution, incubate at room temperature for 15minutes using plateshaker.

Measure the fluorescence in a time-resolved fluorometer by usingVARIOSKAN FLASH. The specific release was calculated using the followingformula:% specific release=Experiment release−Spontaneous release/Maximumrelease−Spontaneous release

Results: we followed the above to determine the effect on cytotoxicityof the CD328 knockdown. The results of one representative experiment areshown in FIG. 9. As seen, cytotoxicity against target cells wasincreased in cells with the CD328 knockdown.

Example 5—Protocol for Blood Cancer Therapy by Knockdown/Knockout ofCheckpoint Inhibitory Receptors

As demonstrated in the above Examples, checkpoint inhibitory receptorfunction can be knocked down or knocked out in a variety of ways. Thefollowing protocol was developed for use in treating patients with bloodcancer:

Following diagnosis of a patient with a cancer suitably treated with theinvention, an aliquot of modified NK cells can be thawed and culturedprior to administration to the patient.

Alternatively, a transient mutation can be prepared using e.g. siRNAwithin a day or two, as described above. The MaxCyte FlowElectroporation platform offers a suitable solution for achieving fastlarge-scale transfections in the clinic.

The removal of certain checkpoint inhibitory receptors may be morebeneficial than others. This is likely to depend on the patient and thecancer. For this reason, the cancer is optionally biopsied and thecancer cells are grown in culture ex vivo. A range of NK cells withdifferent checkpoint inhibitory receptor modifications can thus betested for cytotoxicity against the specific cancer. This step can beused to select the most appropriate NK cell or derivative thereof fortherapy.

Following successful modification, the cells are resuspended in asuitable carrier (e.g. saline) for intravenous and/or intratumoralinjection into the patient.

Example 6—KHYG-1 Knock-in of TRAIL/TRAIL Variant

KHYG-1 cells were transfected with both TRAIL and TRAIL variant, inorder to assess their viability and ability to kill cancer cellsfollowing transfection.

The TRAIL variant used is that described in WO 2009/077857. It isencoded by the wildtype TRAIL gene containing the D269H/E195R mutation.This mutation significantly increases the affinity of the TRAIL variantfor DR5, whilst reducing the affinity for both decoy receptors (DcR1 andDcR2).

Baseline TRAIL Expression

Baseline TRAIL (CD253) expression in KHYG-1 cells was assayed using flowcytometry.

Mouse anti-human CD253-APC (Biolegend catalog number: 308210) andisotype control (Biolegend catalog number: 400122) were used to staincell samples and were analyzed on a BD FACS Canto II flow cytometer.

KHYG-1 cells were cultured in RPMI 1640 medium containing 10% FBS, 2 mML-glutamine, penicillin (100 U/mL)/streptomycin (100 mg/mL) and IL-2 (10ng/mL). 0.5-1.0×10⁶ cells/test were collected by centrifugation (1500rpm×5 minutes) and the supernatant was aspirated. The cells (single cellsuspension) were washed with 4 mL ice cold FACS Buffer (PBS, 0.5-1% BSA,0.1% NaN3 sodium azide). The cells were re-suspended in 100 μL ice coldFACS Buffer, add 5 uL antibody was added to each tube and incubated for30 minutes on ice. The cells were washed 3 times by centrifugation at1500 rpm for 5 minutes. The cells were then re-suspended in 500 μL icecold FACS Buffer and temporarily kept in the dark on ice.

The cells were subsequently analyzed on the flow cytometer (BD FACSCanto II) and the generated data were processed using FlowJo 7.6.2software.

As can be seen in FIG. 10, FACS analysis showed weak baseline expressionof TRAIL on the KHYG-1 cell surface.

TRAIL/TRAIL Variant Knock-in by Electroporation

Wildtype TRAIL mRNA and TRAIL variant (D269H/195R) mRNA was synthesizedby TriLink BioTechnologies, aliquoted and stored as −80° C. Mouseanti-human CD253-APC (Biolegend catalog number: 308210) and isotypecontrol (Biolegend catalog number: 400122), and Mouse anti-humanCD107a-PE (eBioscience catalog number: 12-1079-42) and isotype control(eBioscience catalog number: 12-4714) antibodies were used to stain cellsamples and were analyzed on a BD FACS Canto II flow cytometer. DNA dyeSYTOX-Green (Life Technologies catalog number: S7020; 5 mM Solution inDMSO) was used. To achieve transfection efficiencies of up to 90% withhigh cell viability in KHYG-1 cells with the Nucleofector™ Device(Nucleofector II, Lonza), a Nucleofector™ Kit T from Lonza was used.Antibiotics-free RPMI 1640 containing 10% FBS, L-glutamine (2 mM) andIL-2 (10 ng/mL) was used for post-Nucleofection culture.

KHYG-1 and NK-92 cells were passaged one or two days beforeNucleofection, as the cells must be in the logarithmic growth phase. TheNucleofector solution was pre-warmed to room temperature (100 μl persample), along with an aliquot of culture medium containing serum andsupplements at 37° C. in a 50 mL tube. 6-well plates were prepared byfilling with 1.5 mL culture medium containing serum and supplements andpre-incubated in a humidified 37° C./5% CO₂ incubator. An aliquot ofcell culture was prepared and the cells counted to determine the celldensity. The required number of cells was centrifuged at 1500 rpm for 5min, before discarding the supernatant completely. The cell pellet wasre-suspended in room temperature Nucleofector Solution to a finalconcentration of 2×10⁶ cells/100 μl (maximum time in suspension=20minutes). 100 μl cell suspension was mixed with 10 μg mRNA (volume ofRNA<10 μL). The sample was transferred into an Amaxa-certified cuvette(making sure the sample covered the bottom of the cuvette and avoidingair bubbles). The appropriate Nucleofector program was selected (i.e.U-001 for KHYG-1 cells). The cuvettes were then inserted into thecuvette holder. 500 μl pre-warmed culture medium was added to thecuvette and the sample transferred into a prepared 6-well plateimmediately after the program had finished, in order to avoid damage tothe cells. The cells were incubated in a humidified 37° C./5% CO₂incubator. Flow cytometric analysis and cytotoxicity assays wereperformed 12-16 hours after electroporation. Flow cytometry staining wascarried out as above.

As can be seen in FIGS. 11 and 12, expression of TRAIL/TRAIL variant andCD107a (NK activation marker) increased post-transfection, confirmingthe successful knock-in of the TRAIL genes into KHYG-1 cells.

FIG. 13 provides evidence of KHYG-1 cell viability before and aftertransfection via electroporation. It can be seen that no statisticallysignificant differences in cell viability are observed followingtransfection of the cells with TRAIL/TRAIL variant, confirming that theexpression of wildtype or variant TRAIL is not toxic to the cells. Thisobservation contradicts corresponding findings in NK-92 cells, whichsuggest the TRAIL variant gene knock-in is toxic to the cells (data notshown). Nevertheless, this is likely explained by the relatively highexpression levels of TRAIL receptors DR4 and DR5 on the NK-92 cellsurface (see FIG. 14).

Effects of TRAIL/TRAIL Variant on KHYG-1 Cell Cytotoxicity

Mouse anti-human CD2-APC antibody (BD Pharmingen catalog number: 560642)was used. Annexin V-FITC antibody (ImmunoTools catalog number: 31490013)was used. DNA dye SYTOX-Green (Life Technologies catalog number: S7020)was used. A 24-well cell culture plate (SARSTEDT AG catalog number:83.3922) was used. Myelogenous leukemia cell line K562, multiple myelomacell line RPMI8226 and MM1.S were used as target cells. K562, RPMI8226,MM1.S were cultured in RPMI 1640 medium containing 10% FBS, 2 mML-glutamine and penicillin (100 U/mL)/streptomycin (100 mg/mL).

As explained above, KHYG-1 cells were transfected with TRAIL/TRAILvariant.

The target cells were washed and pelleted via centrifugation at 1500 rpmfor 5 minutes. Transfected KHYG-1 cells were diluted to 0.5×10⁶/mL. Thetarget cell density was then adjusted in pre-warmed RPMI 1640 medium, inorder to produce effector:target (E:T) ratios of 1:1.

0.5 mL KHYG-1 cells and 0.5 mL target cells were then mixed in a 24-wellculture plate and placed in a humidified 37° C./5% CO₂ incubator for 12hours. Flow cytometric analysis was then used to assay KHYG-1 cellcytotoxicity; co-cultured cells (at different time points) were washedand then stained with CD2-APC antibody (5 μL/test), Annexin V-FITC (5μL/test) and SYTOX-Green (5 μL/test) using Annexin V binding buffer.

Data were further analyzed using FlowJo 7.6.2 software. CD2-positive andCD2-negative gates were set, which represent KHYG-1 cell and target cellpopulations, respectively. The Annexin V-FITC and SYTOX-Green positivecells in the CD2-negative population were then analyzed forTRAIL-induced apoptosis.

FIGS. 15, 16 and 17 show the effects of both KHYG-1 cells expressingTRAIL or TRAIL variant on apoptosis for the three target cell lines:K562, RPMI8226 and MM1.S, respectively. It is apparent for all targetcell populations that TRAIL expression on KHYG-1 cells increased thelevel of apoptosis, when compared to normal KHYG-1 cells (nottransfected with TRAIL). Moreover, TRAIL variant expression on KHYG-1cells further increased apoptosis in all target cell lines, whencompared to KHYG-1 cells transfected with wildtype TRAIL.

Cells of the invention, expressing the TRAIL variant, offer asignificant advantage in cancer therapy, due to exhibiting higheraffinities for the death receptor DR5. When challenged by these cells ofthe invention, cancer cells are prevented from developing defensivestrategies to circumvent death via a certain pathway. Thus cancerscannot effectively circumvent TRAIL-induced cell death by upregulatingTRAIL decoy receptors, as cells of the invention are modified so thatthey remain cytotoxic in those circumstances.

Example 7—Protocol for Blood Cancer Therapy Using NK Cells with TRAILVariants Knocked-in

KHYG-1 cells were transfected with TRAIL variant, as described above inExample 6. The following protocol was developed for use in treatingpatients with blood cancer:

Following diagnosis of a patient with a cancer suitably treated with theinvention, a DR5-inducing agent, e.g. Bortezomib, is administered, priorto administration of the modified NK cells, and hence is used at lowdoses to upregulate expression of DR5 on the cancer, making modified NKcell therapy more effective.

An aliquot of modified NK cells is then thawed, cultured andadministered to the patient.

Since the TRAIL variant expressed by the NK cells used in therapy has alower affinity for decoy receptors than wildtype TRAIL, there isincreased binding of death receptors on the cancer cell surface, andhence more cancer cell apoptosis as a result.

Another option, prior to implementation of the above protocol, is tobiopsy the cancer and culture cancer cells ex vivo. This step can beused to identify those cancers expressing particularly high levels ofdecoy receptors, and/or low levels of death receptors, in order to helpdetermine whether a DR5-inducing agent is appropriate for a givenpatient. This step may also be carried out during therapy with the aboveprotocol, as a given cancer might be capable of adapting to e.g. reduceits expression of DR5, and hence it may become suitable to treat with aDR5-inducing agent part-way through therapy.

Example 8—Low Dose Bortezomib Sensitizes Cancer Cells to NK CellsExpressing TRAIL Variant

Bortezomib (Bt) is a proteasome inhibitor (chemotherapy-like drug)useful in the treatment of Multiple Myeloma (MM). Bortezomib is known toupregulate DR5 expression on several different types of cancer cells,including MM cells.

KHYG-1 cells were transfected with TRAIL variant, as described above inExample 6, before being used to target MM cells with or without exposureto Bortezomib.

Bortezomib-Induced DR5 Expression

Bortezomib was bought from Millennium Pharmaceuticals. Mouse anti-humanDR5-AF647 (catalog number: 565498) was bought from BD Pharmingen. Thestained cell samples were analyzed on BD FACS Canto II.

(1) MM cell lines RPMI8226 and MM1.S were grown in RPMI1640 medium(Sigma, St Louis, Mo., USA) supplemented with 2 mM L-glutamine, 10 mMHEPES, 24 mM sodium bicarbonate, 0.01% of antibiotics and 10% fetalbovine serum (Sigma, St Louis, Mo., USA), in 5% CO2 atmosphere at 37° C.

(2) MM cells were seeded in 6-well plates at 1×10⁶/mL, 2 mL/well.

(3) MM cells were then treated with different doses of Bortezomib for 24hours.

(4) DR5 expression in Bortezomib treated/untreated MM cells was thenanalyzed by flow cytometry (FIG. 18).

Low dose Bortezomib treatment was found to increase DR5 expression inboth MM cell lines (FIG. 18). DR5 upregulation was associated with aminor induction of apoptosis (data not shown). It was found, however,that DR5 expression could not be upregulated by high doses ofBortezomib, due to high toxicity resulting in most of the MM cellsdying.

Bortezomib-Induced Sensitization of Cancer Cells

KHYG-1 cells were transfected with the TRAIL variant (TRAILD269H/E195R), as described above in Example 6.

(1) Bortezomib treated/untreated MM1.S cells were used as target cells.MM1.S cells were treated with 2.5 nM of Bortzeomib or vehicle (control)for 24 hours.

(2) 6 hours after electroporation of TRAIL variant mRNA, KHYG-1 cellswere then cultured with MM cells in 12-well plate. After washing, cellconcentrations were adjusted to 1×10⁶/mL, before mixing KHYG-1 and MM1.Scells at 1:1 ratio to culture for 12 hours.

(3) Flow cytometric analysis of the cytotoxicity of KHYG-1 cells wascarried out. The co-cultured cells were collected, washed and thenstained with CD2-APC antibody (5 uL/test), AnnexinV-FITC (5 uL/test) andSYTOX-Green (5 uL/test) using AnnexinV binding buffer.

(4) Data were further analyzed using FlowJo 7.6.2 software. CD2-negativepopulation represents MM1.S cells. KHYG-1 cells are strongly positivefor CD2. Finally, the AnnexinV-FITC and SYTOX-Green positive cells inthe CD2-negative population were analyzed.

Flow cytometric analysis of apoptosis was performed inBortezomib-pretreated/untreated MM1.S cells co-cultured with KHYG-1cells electroporated with/without TRAIL variant (FIG. 19).

It was found that Bortezomib induced sensitivity of MM cells to KHYG-1cells expressing the TRAIL variant. The data therefore indicated that anagent that induced DR5 expression was effective in the model inincreasing cytotoxicity against cancer cells, and hence may be useful inenhancing the cancer therapy of the present invention.

Example 9—Confirmation of Induced Apoptosis by the TRAIL Variant

Despite the conclusive evidence of increased NK cell cytotoxicityresulting from TRAIL variant expression in the previous Examples, wewished to confirm whether the increased cytotoxicity resulted frominducing cancer cell apoptosis (most likely) or by inadvertentlyactivating the NK cells to exhibit a more cytotoxic phenotype and hencekill cancer cells via perforin secretion.

Concanamycin A (CMA) has been demonstrated to inhibit perforin-mediatedcytotoxic activity of NK cells, mostly due to accelerated degradation ofperforin by an increase in the pH of lytic granules. We investigatedwhether the cytotoxicity of KHYG-1 cells expressing the TRAIL variantcould be highlighted when perforin-mediated cytotoxicity was partiallyabolished with CMA.

CMA-Induced Reduction of Perforin Expression

Mouse anti-human perforin-AF647 (catalog number: 563576) was bought fromBD pharmingen. Concanamycin A (catalog number: SC-202111) was boughtfrom Santa Cruz Biotechnology. The stained cell samples were analyzedusing a BD FACS Canto II.

(1) KHYG-1 cells were cultured in RPMI1640 medium containing 10% FBS(fetal bovine serum), 2 mM L-glutamine, penicillin (100U/mL)/streptomycin (100 mg/mL), and IL-2 (10 ng/mL).

(2) KHYG-1 cells (6 hours after electroporation, cultured inpenicillin/streptomycin free RPMI1640 medium) were further treated with100 nM CMA or equal volume of vehicle (DMSO) for 2 hours.

(3) The cells were collected (1×10⁶ cells/test) by centrifugation (1500rpm×5 minutes) and the supernatant was aspirated.

(4) The cells were fixed in 4% paraformaldehyde in PBS solution at roomtemperature for 15 minutes.

(5) The cells were washed with 4 mL of FACS Buffer (PBS, 0.5-1% BSA,0.1% sodium azide) twice.

(6) The cells were permeabilized with 1 mL of PBS/0.1% saponin bufferfor 30 minutes at room temperature.

(7) The cells were washed with 4 mL of PBS/0.1% saponin buffer.

(8) The cells were re-suspended in 100 uL of PBS/0.1% saponin buffer,before adding 5 uL of the antibody to each tube and incubating for 30minutes on ice.

(9) The cells were washed with PBS/0.1% saponin buffer 3 times bycentrifugation at 1500 rpm for 5 minutes.

(10) The cells were re-suspended in 500 uL of ice cold FACS Buffer andkept in the dark on ice or at 4° C. in a fridge briefly until analysis.

(11) The cells were analyzed on the flow cytometer (BD FACS Canto II).The data were processed using FlowJo 7.6.2 software.

CMA treatment significantly decreased the perforin expression level inKHYG-1 cells (FIG. 20) and had no negative effects on the viability ofKHYG-1 cells (FIG. 21).

Cytotoxicity of NK Cell TRAIL Variants in the Presence of CMA

KHYG-1 cells were transfected with the TRAIL variant (TRAILD269H/E195R), as described above in Example 6.

(1) MM1.S cells were used as target cells.

(2) 6 hours after electroporation of TRAIL mRNA, KHYG-1 cells weretreated with 100 mM CMA or an equal volume of vehicle for 2 hours.

(3) The KHYG-1 cells were washed with RPMI1640 medium by centrifugation,and re-suspended in RPMI1640 medium containing IL-2, adjusting cellconcentrations to 1×10⁶/mL.

(4) The MM1.S cells were re-suspended in RPMI1640 medium containing IL-2adjusting cell concentrations to 1×10⁶/mL.

(5) The KHYG-1 and MM1.S cells were mixed at 1:1 ratio and co-culturedfor 12 hours.

(6) Flow cytometric analysis of the cytotoxicity of KHYG-1 cells wascarried out. The co-cultured cells were washed and stained with CD2-APCantibody (5 uL/test).

(7) After washing, further staining was performed with AnnexinV-FITC (5uL/test) and SYTOX-Green (5 uL/test) using AnnexinV binding buffer.

(8) Data were further analyzed using FlowJo 7.6.2 software. CD2-negativepopulation represents MM1.S cells. KHYG-1 cells are strongly positivefor CD2. The AnnexinV-FITC and SYTOX-Green positive cells inCD2-negative population were then analyzed.

It was again shown that NK cells expressing the TRAIL variant showhigher cytotoxicity than control cells lacking expression of the TRAILvariant (FIG. 22). In this Example, however, it was further shown thatCMA was unable to significantly diminish the cytotoxic activity of NKcells expressing TRAIL variant, in contrast to the finding for controlNK cells treated with CMA.

NK cells without the TRAIL variant (control or mock NK cells) were shownto induce 48% cancer cell death in the absence CMA and 35.9% cancer celldeath in the presence of CMA (FIG. 22). NK cells expressing the TRAILvariant were able to induce more cancer cell death than control NK cellsboth in the presence and absence of CMA. In fact, even with CMA present,NK cells expressing TRAIL variant induced more cancer cell death thancontrol NK cells in the absence of CMA.

This data thus shows the importance of the TRAIL variant in increasingNK cell cytotoxicity against cancer cells via a mechanism lesssusceptible to perforin-related downregulation. Since perforin is usedcommonly by NK cells to kill target cells, and many cancer cells havedeveloped mechanisms for reducing NK cell perforin expression, in orderto evade cytotoxic attack, the NK cells of the invention represent apowerful alternative less susceptible to attenuation by cancer cells.

Example 10—Combined Expression of Mutant TRAIL Variant and Knockdown ofCheckpoint Inhibitory Receptor CD96 in KHYG-1 Cells

Increases in NK cell cytotoxicity were observed when knocking downcheckpoint inhibitory receptor CD96 expression and also when expressingTRAIL variant. We also tested combining the two genetic modifications toprovoke a synergistic effect on NK cell cytotoxicity.

CD96 expression was knocked down in KHYG-1 cells, as described inExample 2.

KHYG-1 cells were transfected with the TRAIL variant (TRAILD269H/E195R), as described above in Example 6.

(1) 12 hours after electroporation KHYG-1 cells were co-cultured withtarget cells (K562 or MM1.S) at a concentration of 1×10⁶/mL in 12-wellplates (2 mL/well) for 12 hours. The E:T ratio was 1:1.

(2) 12 hours after co-culture, the cells were collected, washed, stainedwith CD2-APC, washed again and further stained with AnnexinV-FITC (5uL/test) and SYTOX-Green (5 uL/test) using AnnexinV binding buffer.

(3) Cell samples were analyzed using a BD FACS canto II flow cytometer.Data were further analyzed using FlowJo 7.6.2 software. CD2-negativepopulation represents MM1.S cells. KHYG-1 cells are strongly positivefor CD2. The AnnexinV-FITC and SYTOX-Green positive cells in theCD2-negative population were then analyzed.

Simultaneously knocking down CD96 expression and expressing TRAILvariant in KHYG-1 cells was found to synergistically enhance the cells'cytotoxicity against both K562 target cells (FIG. 23) and MM1.S targetcells (FIG. 24). This was indicated by the fact that in both target cellgroups, more cell death resulted from the simultaneous geneticmodification than resulted from the individual modifications inisolation.

At the same time, further evidence showing knockdown of CD96 increasesNK cell cytotoxicity was obtained (FIGS. 23 & 24), in addition tofurther evidence showing expression of the TRAIL mutant/variantincreases NK cell cytotoxicity (FIGS. 23 & 24).

The invention thus provides NK cells and cell lines, and productionthereof, for use in blood cancer therapy.

What is claimed is:
 1. A method of treating a DR5-expressing and/orDR5-inducible blood cancer in an individual in need thereof, comprisingadministering to the individual a natural killer (NK) cell or NK cellline modified to express a TRAIL variant, wherein the TRAIL variant hasan increased affinity for a DR5 TRAIL receptor compared to wildtypeTRAIL, and wherein the TRAIL variant comprises mutations D269H andE195R, wherein the blood cancer is a DR5-expressing and/or DR5-inducingblood cancer.
 2. The method of claim 1, wherein the TRAIL variant has areduced affinity for a decoy TRAIL receptor.
 3. The method of claim 1,further comprising administering to the individual an effective amountof a proteasome inhibitor.
 4. The method of claim 3, wherein theproteasome inhibitor is bortezomib.
 5. The method of claim 1, whereinthe NK cell or NK cell line further comprises a modification thatreduces or abolishes expression of a checkpoint inhibitory receptor. 6.The method of claim 5, wherein the checkpoint inhibitory receptor isCD96 (TACTILE), CD152 (CTLA4), CD223 (LAG-3), CD279 (PD-1), CD328(SIGLEC7), SIGLEC9, TIGIT or TIM-3.
 7. The method of claim 1, whereinthe NK cell or NK cell line targets the bone marrow.
 8. The method ofclaim 7, wherein the NK cell or NK cell line further comprise amodification to express fucosyltransferase or sialyltransferase.
 9. Themethod of claim 1, wherein the NK cell line is a KHYG-1 cell line or aderivative thereof.
 10. The method of claim 1, wherein the blood canceris acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML),chronic lymphocytic leukemia (CLL), chronic myeloid leukemia (CML),Hodgkin's lymphoma, non-Hodgkin's lymphoma, T-cell lymphoma, B-celllymphoma, asymptomatic myeloma, multiple myeloma, smoldering multiplemyeloma (SMM), active myeloma, or light chain myeloma.
 11. The method ofclaim 1, wherein the blood cancer is chronic myeloid leukemia ormultiple myeloma.
 12. The method of claim 1, wherein the blood cancer ischronic myeloid leukemia or multiple myeloma, and wherein the NK cellline is a KHYG-1 cell line.